JPS6210093B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a small electronic device having a lighting device, and its purpose is to prevent malfunction of the electronic circuit when the lamp is turned on.

BACKGROUND OF THE INVENTION Some small portable electronic devices powered by ultra-small batteries have lighting devices for convenient use in dark places. For example, most commercially available LCD watches have built-in lighting lamps. A current of several mA or more normally flows through these illumination lamps when they are lit. For this reason, if the internal resistance of the battery used is high, the power supply voltage applied to the electronic circuit during lamp lighting may drop, causing the circuit to malfunction.

The present invention aims to prevent the above-mentioned inconvenience by providing a solar cell so that it can receive the light emitted by the lamp when the lamp is turned on, and connecting it to a circuit to compensate for the drop in battery voltage.

A detailed explanation will be given below based on the drawings. FIG. 1 is a basic configuration diagram of a clock having an illumination device, in which the output of a reference oscillator 1 is supplied to a frequency divider 2,
The output of the frequency divider 2 is supplied to a display drive circuit 3,
A display device 4 is driven by the output of the display drive circuit 3. The control device 5 is electrically or mechanically connected to each of the above-mentioned parts as necessary. The lighting device 6 is connected to the control device 5 and is turned on based on a signal from the control device 5 to illuminate the display device 4 . The circuit configured as described above operates by being supplied with power from a battery 7, but the battery 7 has an internal resistance 8, and when the value of this internal resistance 8 is large, the circuit may malfunction.

That is, since the lighting device 6 consumes considerably larger current than other circuit parts when it is lit, if the value of the internal resistance 8 of the battery 7 is large, the terminal voltage of the battery 7 decreases. A circuit to which the terminal voltage is applied may malfunction or stop.

Conventionally, this type of problem has been the battery voltage drop when the clock pulse motor is driven, but the pulse motor drive time is at most 3 to 8 mSec.
This problem was solved by using a backup capacitor, but when the lighting time of a lighting device is an issue like in this case, it is necessary to allow for several seconds, and if a backup capacitor is used, the value is at least 20 μF. is necessary, and the volume of the capacitor becomes too large, which not only makes it difficult to incorporate it into the watch, but even if it can be inserted into the watch, the lighting time of the lighting device 6 may be longer than the expected value. Considering that this is possible, it is clear that this is not an essential solution.

Therefore, the present invention has been made in order to solve the above-mentioned problems and provide a clock with stable operation without imposing any restrictions on the lighting time of the lighting device 6. When the battery is exposed to electricity, the light is received by a photovoltaic element such as a solar cell, and the voltage generated in the photovoltaic element is used to compensate for the drop in battery voltage, thereby stabilizing the operation of the circuit. be.

FIG. 2 shows a first embodiment of the present invention, in which the high potential side power supply terminal of the compensated circuit section 9 is connected directly, and one terminal of the lighting device 6 is connected via a switch element 10 operated by a push button or the like. A battery 7 having an internal resistance 8
connected to the positive terminal of the The remaining other end of the illumination device 6 is directly applied to the negative electrode of the battery 7, and the low potential side power supply terminal of the compensated circuit portion 9 is connected to a diode 12 and a photovoltaic power whose polarity is in the forward direction with respect to the polarity of the power supply 7. It is connected to the negative electrode of the battery 7 through a parallel circuit consisting of the solar battery 11 as an element.

The above-mentioned compensated circuit portion 9 is the entire circuit,
This refers to a portion that is compensated for the power supply voltage by implementing the present invention, and refers to, for example, the portion indicated by a broken line in FIG.

In FIG. 2, when the switch element 10 is in a non-conductive state, the lighting device 6 does not light up, and therefore the solar cell 11 does not generate an electromotive force based on the lighting device 6.
The current flowing from the positive terminal of the battery 7 passes through the compensated circuit portion 9 and returns to the negative terminal of the battery 7 via the diode 12. Further, when the switch element 10 becomes conductive, the lighting device 6 lights up,
An electromotive force is generated in the installed solar cell 11 so as to receive a part of the luminous flux from the lighting device 6. Since the direction of this electromotive force is such that the low potential side power supply end of the compensated circuit portion 9 has a lower potential when viewed from the negative electrode of the battery 7, the current flows through the solar cell 11 instead of the diode 12. It returns to the battery 7 via the battery. Therefore, even if the voltage across the battery 7 decreases due to the current flowing through the lighting device 6 and the internal resistance 8 of the battery 7, the solar battery 1
1, a sufficiently large voltage is applied to the compensated circuit portion 9, and its operation does not stop.

FIG. 3 shows another embodiment of the present invention, in which the high potential side power supply terminal of the compensated circuit section 9 is directly connected to the positive electrode of the battery 7, and the low potential side power supply terminal of the compensated circuit section 9 is connected directly to the positive electrode of the battery 7. The battery 7 via the diode element 12
It is connected to the negative electrode of the battery 7, and also to the positive electrode of the battery 7 through a series circuit of a backflow prevention diode element 13 whose polarity is opposite to that of the solar cell 11 and the power source 7. The lighting device 6 is the switch element 1
0 to the positive and negative electrodes of the battery 7.

This embodiment is effective when the photovoltaic voltage generated by the solar cell 11 is sufficiently higher than the minimum operating voltage of the compensated circuit portion 9. The lighting device 6
When the lighting device 6 is not lit, power is supplied to the compensated circuit portion 9 from the battery 7, and when the lighting device 6 is lit, power is supplied from the solar cell 11 via the backflow prevention diode 13. be done.

As described above, according to the present invention, even when the lighting device is turned on, the operation of the entire circuit does not stop, so it is possible to provide a product with extremely high reliability, which is highly effective.

In the above description, the embodiment has been described with respect to an electronic watch, but it goes without saying that other small electronic devices may be used, and circuit portions that do not carry out the present invention may coexist. Furthermore, although the expression solar cell is used in the description, other elements may be used as long as they generate electromotive force by light. Further, although the switch element 10 is shown as a mechanical switch in FIGS. 2 and 3, it may be an electronic switch.

[Brief explanation of the drawing]

FIG. 1 is a general configuration diagram of an electronic timepiece, FIG. 2 is a circuit diagram showing an embodiment of the invention, and FIG. 3 is a circuit diagram showing another embodiment of the invention. 6... Lighting device, 7... Power supply, 9... Compensated circuit, 10... Switch element, 11... Photovoltaic element, 12... Diode, 13... Backflow prevention diode.

Claims (1)

[Scope of Claims] 1. An electronic circuit having a display device, a forward diode and a battery connected in series to a power terminal of the electronic circuit, and a light connected to the battery via a switch means to illuminate the display device. and a photovoltaic element that receives a portion of the luminous flux generated by the lighting device, the photovoltaic element being connected in parallel to the diode in a direction in which the electromotive force compensates for the voltage of the battery. A small electronic device having a lighting device characterized in that: 2. An electronic circuit having a display device, a forward diode and a battery connected in series to a power supply terminal of the electronic circuit, a lighting device connected to the battery via a switch means to illuminate the display device, and the lighting device a photovoltaic element that receives a part of the luminous flux generated by the photovoltaic element, and a backflow prevention diode, the photovoltaic element has a polarity of its electromotive force in the same direction as the polarity of the battery and a polarity of the power source. A small electronic device having a lighting device, characterized in that the lighting device is connected in parallel to the power supply terminal via the backflow prevention diode whose direction is opposite to that of the lighting device.